CMS-HIN-18-003 ; CERN-EP-2021-028 | ||
Study of Drell-Yan dimuon production in proton-lead collisions at ${\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 8.16 TeV | ||
CMS Collaboration | ||
26 February 2021 | ||
JHEP 05 (2021) 182 | ||
Abstract: Differential cross sections for the Drell-Yan process, including Z boson production, using the dimuon decay channel are measured in proton-lead (pPb) collisions at a nucleon-nucleon centre-of-mass energy of 8.16 TeV. A data sample recorded with the CMS detector at the LHC is used, corresponding to an integrated luminosity of 173 nb$^{-1}$. The differential cross section as a function of the dimuon mass is measured in the range 15-600 GeV, for the first time in proton-nucleus collisions. It is also reported as a function of dimuon rapidity over the mass ranges 15-60 GeV and 60-120 GeV, and ratios for the p-going over the Pb-going beam directions are built. In both mass ranges, the differential cross sections as functions of the dimuon transverse momentum ${p_{\mathrm{T}}}$ and of a geometric variable ${\phi^*}$ are measured, where ${\phi^*}$ highly correlates with ${p_{\mathrm{T}}}$ but is determined with higher precision. In the Z mass region, the rapidity dependence of the data indicate a modification of the distribution of partons within a lead nucleus as compared to the proton case. The data are more precise than predictions based upon current models of parton distributions. | ||
Links: e-print arXiv:2102.13648 [hep-ex] (PDF) ; CDS record ; inSPIRE record ; HepData record ; CADI line (restricted) ; |
Figures | |
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Figure 1:
Comparison of the data (black points) with the ${\mathrm{Z} /\gamma ^{*}}$ signal and background expectations (filled histograms, where "EW" includes $ {\mathrm{Z} /\gamma ^{*}} \to \tau^{+} \tau^{-} $ and diboson), estimated as described in the text, as a function of invariant mass (upper) and rapidity in the centre-of-mass frame for 15 $ < {m_{\mu \mu}} < $ 60 GeV (lower left) and 60 $ < {m_{\mu \mu}} < $ 120 GeV (lower right). Vertical error bars represent statistical uncertainties. The ratios of data over expectations are shown in the lower panels. The boson ${p_{\mathrm {T}}}$ reweighting described in the text is not applied. The shaded regions show the quadratic sum of the systematic uncertainties (including the integrated luminosity, but excluding acceptance and unfolding uncertainties) and the nPDF uncertainties (CT14+EPPS16). |
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Figure 1-a:
Comparison of the data (black points) with the ${\mathrm{Z} /\gamma ^{*}}$ signal and background expectations (filled histograms, where "EW" includes $ {\mathrm{Z} /\gamma ^{*}} \to \tau^{+} \tau^{-} $ and diboson), estimated as described in the text, as a function of invariant mass (upper) and rapidity in the centre-of-mass frame for 15 $ < {m_{\mu \mu}} < $ 60 GeV (lower left) and 60 $ < {m_{\mu \mu}} < $ 120 GeV (lower right). Vertical error bars represent statistical uncertainties. The ratios of data over expectations are shown in the lower panels. The boson ${p_{\mathrm {T}}}$ reweighting described in the text is not applied. The shaded regions show the quadratic sum of the systematic uncertainties (including the integrated luminosity, but excluding acceptance and unfolding uncertainties) and the nPDF uncertainties (CT14+EPPS16). |
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Figure 1-b:
Comparison of the data (black points) with the ${\mathrm{Z} /\gamma ^{*}}$ signal and background expectations (filled histograms, where "EW" includes $ {\mathrm{Z} /\gamma ^{*}} \to \tau^{+} \tau^{-} $ and diboson), estimated as described in the text, as a function of invariant mass (upper) and rapidity in the centre-of-mass frame for 15 $ < {m_{\mu \mu}} < $ 60 GeV (lower left) and 60 $ < {m_{\mu \mu}} < $ 120 GeV (lower right). Vertical error bars represent statistical uncertainties. The ratios of data over expectations are shown in the lower panels. The boson ${p_{\mathrm {T}}}$ reweighting described in the text is not applied. The shaded regions show the quadratic sum of the systematic uncertainties (including the integrated luminosity, but excluding acceptance and unfolding uncertainties) and the nPDF uncertainties (CT14+EPPS16). |
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Figure 1-c:
Comparison of the data (black points) with the ${\mathrm{Z} /\gamma ^{*}}$ signal and background expectations (filled histograms, where "EW" includes $ {\mathrm{Z} /\gamma ^{*}} \to \tau^{+} \tau^{-} $ and diboson), estimated as described in the text, as a function of invariant mass (upper) and rapidity in the centre-of-mass frame for 15 $ < {m_{\mu \mu}} < $ 60 GeV (lower left) and 60 $ < {m_{\mu \mu}} < $ 120 GeV (lower right). Vertical error bars represent statistical uncertainties. The ratios of data over expectations are shown in the lower panels. The boson ${p_{\mathrm {T}}}$ reweighting described in the text is not applied. The shaded regions show the quadratic sum of the systematic uncertainties (including the integrated luminosity, but excluding acceptance and unfolding uncertainties) and the nPDF uncertainties (CT14+EPPS16). |
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Figure 2:
Comparison of the data (black points) with the ${\mathrm{Z} /\gamma ^{*}}$ signal and background expectations (filled histograms, where "EW" includes $ {\mathrm{Z} /\gamma ^{*}} \to \tau^{+} \tau^{-} $ and diboson), estimated as described in the text, as a function of ${p_{\mathrm {T}}}$ (upper row) and ${\phi ^*}$ (lower row), for 15 $ < {m_{\mu \mu}} < $ 60 GeV (left) and 60 $ < {m_{\mu \mu}} < $ 120 GeV (right). The first bins of the ${p_{\mathrm {T}}}$ and ${\phi ^*}$ distributions start at 0. Vertical error bars represent statistical uncertainties. The ratios of data over expectations are shown in the lower panels. The boson ${p_{\mathrm {T}}}$ reweighting described in the text is not applied. The shaded regions show the quadratic sum of the systematic uncertainties (including the integrated luminosity, but excluding acceptance and unfolding uncertainties) and the nPDF uncertainties (CT14+EPPS16). |
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Figure 2-a:
Comparison of the data (black points) with the ${\mathrm{Z} /\gamma ^{*}}$ signal and background expectations (filled histograms, where "EW" includes $ {\mathrm{Z} /\gamma ^{*}} \to \tau^{+} \tau^{-} $ and diboson), estimated as described in the text, as a function of ${p_{\mathrm {T}}}$ (upper row) and ${\phi ^*}$ (lower row), for 15 $ < {m_{\mu \mu}} < $ 60 GeV (left) and 60 $ < {m_{\mu \mu}} < $ 120 GeV (right). The first bins of the ${p_{\mathrm {T}}}$ and ${\phi ^*}$ distributions start at 0. Vertical error bars represent statistical uncertainties. The ratios of data over expectations are shown in the lower panels. The boson ${p_{\mathrm {T}}}$ reweighting described in the text is not applied. The shaded regions show the quadratic sum of the systematic uncertainties (including the integrated luminosity, but excluding acceptance and unfolding uncertainties) and the nPDF uncertainties (CT14+EPPS16). |
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Figure 2-b:
Comparison of the data (black points) with the ${\mathrm{Z} /\gamma ^{*}}$ signal and background expectations (filled histograms, where "EW" includes $ {\mathrm{Z} /\gamma ^{*}} \to \tau^{+} \tau^{-} $ and diboson), estimated as described in the text, as a function of ${p_{\mathrm {T}}}$ (upper row) and ${\phi ^*}$ (lower row), for 15 $ < {m_{\mu \mu}} < $ 60 GeV (left) and 60 $ < {m_{\mu \mu}} < $ 120 GeV (right). The first bins of the ${p_{\mathrm {T}}}$ and ${\phi ^*}$ distributions start at 0. Vertical error bars represent statistical uncertainties. The ratios of data over expectations are shown in the lower panels. The boson ${p_{\mathrm {T}}}$ reweighting described in the text is not applied. The shaded regions show the quadratic sum of the systematic uncertainties (including the integrated luminosity, but excluding acceptance and unfolding uncertainties) and the nPDF uncertainties (CT14+EPPS16). |
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Figure 2-c:
Comparison of the data (black points) with the ${\mathrm{Z} /\gamma ^{*}}$ signal and background expectations (filled histograms, where "EW" includes $ {\mathrm{Z} /\gamma ^{*}} \to \tau^{+} \tau^{-} $ and diboson), estimated as described in the text, as a function of ${p_{\mathrm {T}}}$ (upper row) and ${\phi ^*}$ (lower row), for 15 $ < {m_{\mu \mu}} < $ 60 GeV (left) and 60 $ < {m_{\mu \mu}} < $ 120 GeV (right). The first bins of the ${p_{\mathrm {T}}}$ and ${\phi ^*}$ distributions start at 0. Vertical error bars represent statistical uncertainties. The ratios of data over expectations are shown in the lower panels. The boson ${p_{\mathrm {T}}}$ reweighting described in the text is not applied. The shaded regions show the quadratic sum of the systematic uncertainties (including the integrated luminosity, but excluding acceptance and unfolding uncertainties) and the nPDF uncertainties (CT14+EPPS16). |
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Figure 2-d:
Comparison of the data (black points) with the ${\mathrm{Z} /\gamma ^{*}}$ signal and background expectations (filled histograms, where "EW" includes $ {\mathrm{Z} /\gamma ^{*}} \to \tau^{+} \tau^{-} $ and diboson), estimated as described in the text, as a function of ${p_{\mathrm {T}}}$ (upper row) and ${\phi ^*}$ (lower row), for 15 $ < {m_{\mu \mu}} < $ 60 GeV (left) and 60 $ < {m_{\mu \mu}} < $ 120 GeV (right). The first bins of the ${p_{\mathrm {T}}}$ and ${\phi ^*}$ distributions start at 0. Vertical error bars represent statistical uncertainties. The ratios of data over expectations are shown in the lower panels. The boson ${p_{\mathrm {T}}}$ reweighting described in the text is not applied. The shaded regions show the quadratic sum of the systematic uncertainties (including the integrated luminosity, but excluding acceptance and unfolding uncertainties) and the nPDF uncertainties (CT14+EPPS16). |
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Figure 3:
Correlation matrix for the systematic uncertainties, excluding integrated luminosity, as a function of the dimuon invariant mass (upper) and rapidity in the centre-of-mass frame for 15 $ < {m_{\mu \mu}} < $ 60 GeV (lower left) and 60 $ < {m_{\mu \mu}} < $ 120 GeV (lower right). |
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Figure 3-a:
Correlation matrix for the systematic uncertainties, excluding integrated luminosity, as a function of the dimuon invariant mass (upper) and rapidity in the centre-of-mass frame for 15 $ < {m_{\mu \mu}} < $ 60 GeV (lower left) and 60 $ < {m_{\mu \mu}} < $ 120 GeV (lower right). |
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Figure 3-b:
Correlation matrix for the systematic uncertainties, excluding integrated luminosity, as a function of the dimuon invariant mass (upper) and rapidity in the centre-of-mass frame for 15 $ < {m_{\mu \mu}} < $ 60 GeV (lower left) and 60 $ < {m_{\mu \mu}} < $ 120 GeV (lower right). |
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Figure 3-c:
Correlation matrix for the systematic uncertainties, excluding integrated luminosity, as a function of the dimuon invariant mass (upper) and rapidity in the centre-of-mass frame for 15 $ < {m_{\mu \mu}} < $ 60 GeV (lower left) and 60 $ < {m_{\mu \mu}} < $ 120 GeV (lower right). |
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Figure 4:
Correlation matrices for the systematic uncertainties, excluding integrated luminosity, as functions of ${p_{\mathrm {T}}}$ (upper row) and ${\phi ^*}$ (lower row), for 15 $ < {m_{\mu \mu}} < $ 60 GeV (left) and 60 $ < {m_{\mu \mu}} < $ 120 GeV (right). |
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Figure 4-a:
Correlation matrices for the systematic uncertainties, excluding integrated luminosity, as functions of ${p_{\mathrm {T}}}$ (upper row) and ${\phi ^*}$ (lower row), for 15 $ < {m_{\mu \mu}} < $ 60 GeV (left) and 60 $ < {m_{\mu \mu}} < $ 120 GeV (right). |
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Figure 4-b:
Correlation matrices for the systematic uncertainties, excluding integrated luminosity, as functions of ${p_{\mathrm {T}}}$ (upper row) and ${\phi ^*}$ (lower row), for 15 $ < {m_{\mu \mu}} < $ 60 GeV (left) and 60 $ < {m_{\mu \mu}} < $ 120 GeV (right). |
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Figure 4-c:
Correlation matrices for the systematic uncertainties, excluding integrated luminosity, as functions of ${p_{\mathrm {T}}}$ (upper row) and ${\phi ^*}$ (lower row), for 15 $ < {m_{\mu \mu}} < $ 60 GeV (left) and 60 $ < {m_{\mu \mu}} < $ 120 GeV (right). |
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Figure 4-d:
Correlation matrices for the systematic uncertainties, excluding integrated luminosity, as functions of ${p_{\mathrm {T}}}$ (upper row) and ${\phi ^*}$ (lower row), for 15 $ < {m_{\mu \mu}} < $ 60 GeV (left) and 60 $ < {m_{\mu \mu}} < $ 120 GeV (right). |
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Figure 5:
Differential fiducial cross section (without the acceptance correction) for the DY process measured in the muon channel, as a function of the dimuon invariant mass (upper) and rapidity in the centre-of-mass frame for 15 $ < {m_{\mu \mu}} < $ 60 GeV (lower left) and 60 $ < {m_{\mu \mu}} < $ 120 GeV (lower right). The error bars on the data represent the quadratic sum of the statistical and systematic uncertainties. Theory predictions from the POWHEG NLO generator are also shown, using CT14 (blue) or CT14+EPPS16 (red). The boxes show the 68% confidence level (n)PDF uncertainty on these predictions. The ratios of predictions over data are shown in the lower panels, where the data and (n)PDF uncertainties are shown separately, as error bars around one and as coloured boxes, respectively. |
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Figure 5-a:
Differential fiducial cross section (without the acceptance correction) for the DY process measured in the muon channel, as a function of the dimuon invariant mass (upper) and rapidity in the centre-of-mass frame for 15 $ < {m_{\mu \mu}} < $ 60 GeV (lower left) and 60 $ < {m_{\mu \mu}} < $ 120 GeV (lower right). The error bars on the data represent the quadratic sum of the statistical and systematic uncertainties. Theory predictions from the POWHEG NLO generator are also shown, using CT14 (blue) or CT14+EPPS16 (red). The boxes show the 68% confidence level (n)PDF uncertainty on these predictions. The ratios of predictions over data are shown in the lower panels, where the data and (n)PDF uncertainties are shown separately, as error bars around one and as coloured boxes, respectively. |
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Figure 5-b:
Differential fiducial cross section (without the acceptance correction) for the DY process measured in the muon channel, as a function of the dimuon invariant mass (upper) and rapidity in the centre-of-mass frame for 15 $ < {m_{\mu \mu}} < $ 60 GeV (lower left) and 60 $ < {m_{\mu \mu}} < $ 120 GeV (lower right). The error bars on the data represent the quadratic sum of the statistical and systematic uncertainties. Theory predictions from the POWHEG NLO generator are also shown, using CT14 (blue) or CT14+EPPS16 (red). The boxes show the 68% confidence level (n)PDF uncertainty on these predictions. The ratios of predictions over data are shown in the lower panels, where the data and (n)PDF uncertainties are shown separately, as error bars around one and as coloured boxes, respectively. |
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Figure 5-c:
Differential fiducial cross section (without the acceptance correction) for the DY process measured in the muon channel, as a function of the dimuon invariant mass (upper) and rapidity in the centre-of-mass frame for 15 $ < {m_{\mu \mu}} < $ 60 GeV (lower left) and 60 $ < {m_{\mu \mu}} < $ 120 GeV (lower right). The error bars on the data represent the quadratic sum of the statistical and systematic uncertainties. Theory predictions from the POWHEG NLO generator are also shown, using CT14 (blue) or CT14+EPPS16 (red). The boxes show the 68% confidence level (n)PDF uncertainty on these predictions. The ratios of predictions over data are shown in the lower panels, where the data and (n)PDF uncertainties are shown separately, as error bars around one and as coloured boxes, respectively. |
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Figure 6:
Differential fiducial cross sections (without the acceptance correction) for the DY process measured in the muon channel, as functions of ${p_{\mathrm {T}}}$ (upper row) and ${\phi ^*}$ (lower row), for 15 $ < {m_{\mu \mu}} < $ 60 GeV (left) and 60 $ < {m_{\mu \mu}} < $ 120 GeV (right). The first bin of the ${p_{\mathrm {T}}}$ and ${\phi ^*}$ measurements starts at 0. The error bars on the data represent the quadratic sum of the statistical and systematic uncertainties. Theory predictions from the POWHEG NLO generator are also shown, using CT14 (blue) or CT14+EPPS16 (red). The boxes show the 68% confidence level (n)PDF uncertainty on these predictions. The ratios of predictions over data are shown in the lower panels, where the data and (n)PDF uncertainties are shown separately, as error bars around one and as coloured boxes, respectively. |
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Figure 6-a:
Differential fiducial cross sections (without the acceptance correction) for the DY process measured in the muon channel, as functions of ${p_{\mathrm {T}}}$ (upper row) and ${\phi ^*}$ (lower row), for 15 $ < {m_{\mu \mu}} < $ 60 GeV (left) and 60 $ < {m_{\mu \mu}} < $ 120 GeV (right). The first bin of the ${p_{\mathrm {T}}}$ and ${\phi ^*}$ measurements starts at 0. The error bars on the data represent the quadratic sum of the statistical and systematic uncertainties. Theory predictions from the POWHEG NLO generator are also shown, using CT14 (blue) or CT14+EPPS16 (red). The boxes show the 68% confidence level (n)PDF uncertainty on these predictions. The ratios of predictions over data are shown in the lower panels, where the data and (n)PDF uncertainties are shown separately, as error bars around one and as coloured boxes, respectively. |
png pdf |
Figure 6-b:
Differential fiducial cross sections (without the acceptance correction) for the DY process measured in the muon channel, as functions of ${p_{\mathrm {T}}}$ (upper row) and ${\phi ^*}$ (lower row), for 15 $ < {m_{\mu \mu}} < $ 60 GeV (left) and 60 $ < {m_{\mu \mu}} < $ 120 GeV (right). The first bin of the ${p_{\mathrm {T}}}$ and ${\phi ^*}$ measurements starts at 0. The error bars on the data represent the quadratic sum of the statistical and systematic uncertainties. Theory predictions from the POWHEG NLO generator are also shown, using CT14 (blue) or CT14+EPPS16 (red). The boxes show the 68% confidence level (n)PDF uncertainty on these predictions. The ratios of predictions over data are shown in the lower panels, where the data and (n)PDF uncertainties are shown separately, as error bars around one and as coloured boxes, respectively. |
png pdf |
Figure 6-c:
Differential fiducial cross sections (without the acceptance correction) for the DY process measured in the muon channel, as functions of ${p_{\mathrm {T}}}$ (upper row) and ${\phi ^*}$ (lower row), for 15 $ < {m_{\mu \mu}} < $ 60 GeV (left) and 60 $ < {m_{\mu \mu}} < $ 120 GeV (right). The first bin of the ${p_{\mathrm {T}}}$ and ${\phi ^*}$ measurements starts at 0. The error bars on the data represent the quadratic sum of the statistical and systematic uncertainties. Theory predictions from the POWHEG NLO generator are also shown, using CT14 (blue) or CT14+EPPS16 (red). The boxes show the 68% confidence level (n)PDF uncertainty on these predictions. The ratios of predictions over data are shown in the lower panels, where the data and (n)PDF uncertainties are shown separately, as error bars around one and as coloured boxes, respectively. |
png pdf |
Figure 6-d:
Differential fiducial cross sections (without the acceptance correction) for the DY process measured in the muon channel, as functions of ${p_{\mathrm {T}}}$ (upper row) and ${\phi ^*}$ (lower row), for 15 $ < {m_{\mu \mu}} < $ 60 GeV (left) and 60 $ < {m_{\mu \mu}} < $ 120 GeV (right). The first bin of the ${p_{\mathrm {T}}}$ and ${\phi ^*}$ measurements starts at 0. The error bars on the data represent the quadratic sum of the statistical and systematic uncertainties. Theory predictions from the POWHEG NLO generator are also shown, using CT14 (blue) or CT14+EPPS16 (red). The boxes show the 68% confidence level (n)PDF uncertainty on these predictions. The ratios of predictions over data are shown in the lower panels, where the data and (n)PDF uncertainties are shown separately, as error bars around one and as coloured boxes, respectively. |
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Figure 7:
Differential cross section for the DY process measured in the muon channel, as a function of the dimuon invariant mass (upper) and rapidity in the centre-of-mass frame for 15 $ < {m_{\mu \mu}} < $ 60 GeV (lower left) and 60 $ < {m_{\mu \mu}} < $ 120 GeV (lower right). The error bars on the data represent the quadratic sum of the statistical and systematic uncertainties. Theory predictions from the POWHEG NLO generator are also shown, using CT14 (blue) or CT14+EPPS16 (red). The boxes show the 68% confidence level (n)PDF uncertainty on these predictions. The ratios of predictions over data are shown in the lower panels, where the data and (n)PDF uncertainties are shown separately, as error bars around one and as coloured boxes, respectively. |
png pdf |
Figure 7-a:
Differential cross section for the DY process measured in the muon channel, as a function of the dimuon invariant mass (upper) and rapidity in the centre-of-mass frame for 15 $ < {m_{\mu \mu}} < $ 60 GeV (lower left) and 60 $ < {m_{\mu \mu}} < $ 120 GeV (lower right). The error bars on the data represent the quadratic sum of the statistical and systematic uncertainties. Theory predictions from the POWHEG NLO generator are also shown, using CT14 (blue) or CT14+EPPS16 (red). The boxes show the 68% confidence level (n)PDF uncertainty on these predictions. The ratios of predictions over data are shown in the lower panels, where the data and (n)PDF uncertainties are shown separately, as error bars around one and as coloured boxes, respectively. |
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Figure 7-b:
Differential cross section for the DY process measured in the muon channel, as a function of the dimuon invariant mass (upper) and rapidity in the centre-of-mass frame for 15 $ < {m_{\mu \mu}} < $ 60 GeV (lower left) and 60 $ < {m_{\mu \mu}} < $ 120 GeV (lower right). The error bars on the data represent the quadratic sum of the statistical and systematic uncertainties. Theory predictions from the POWHEG NLO generator are also shown, using CT14 (blue) or CT14+EPPS16 (red). The boxes show the 68% confidence level (n)PDF uncertainty on these predictions. The ratios of predictions over data are shown in the lower panels, where the data and (n)PDF uncertainties are shown separately, as error bars around one and as coloured boxes, respectively. |
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Figure 7-c:
Differential cross section for the DY process measured in the muon channel, as a function of the dimuon invariant mass (upper) and rapidity in the centre-of-mass frame for 15 $ < {m_{\mu \mu}} < $ 60 GeV (lower left) and 60 $ < {m_{\mu \mu}} < $ 120 GeV (lower right). The error bars on the data represent the quadratic sum of the statistical and systematic uncertainties. Theory predictions from the POWHEG NLO generator are also shown, using CT14 (blue) or CT14+EPPS16 (red). The boxes show the 68% confidence level (n)PDF uncertainty on these predictions. The ratios of predictions over data are shown in the lower panels, where the data and (n)PDF uncertainties are shown separately, as error bars around one and as coloured boxes, respectively. |
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Figure 8:
Differential cross sections for the DY process measured in the muon channel, as functions of ${p_{\mathrm {T}}}$ (upper row) and ${\phi ^*}$ (lower row), for 15 $ < {m_{\mu \mu}} < $ 60 GeV (left) and 60 $ < {m_{\mu \mu}} < $ 120 GeV (right). The first bin of the ${p_{\mathrm {T}}}$ and ${\phi ^*}$ measurements starts at 0. The error bars on the data represent the quadratic sum of the statistical and systematic uncertainties. Theory predictions from the POWHEG NLO generator are also shown, using CT14 (blue) or CT14+EPPS16 (red). The boxes show the 68% confidence level (n)PDF uncertainty on these predictions. The ratios of predictions over data are shown in the lower panels, where the data and (n)PDF uncertainties are shown separately, as error bars around one and as coloured boxes, respectively. |
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Figure 8-a:
Differential cross sections for the DY process measured in the muon channel, as functions of ${p_{\mathrm {T}}}$ (upper row) and ${\phi ^*}$ (lower row), for 15 $ < {m_{\mu \mu}} < $ 60 GeV (left) and 60 $ < {m_{\mu \mu}} < $ 120 GeV (right). The first bin of the ${p_{\mathrm {T}}}$ and ${\phi ^*}$ measurements starts at 0. The error bars on the data represent the quadratic sum of the statistical and systematic uncertainties. Theory predictions from the POWHEG NLO generator are also shown, using CT14 (blue) or CT14+EPPS16 (red). The boxes show the 68% confidence level (n)PDF uncertainty on these predictions. The ratios of predictions over data are shown in the lower panels, where the data and (n)PDF uncertainties are shown separately, as error bars around one and as coloured boxes, respectively. |
png pdf |
Figure 8-b:
Differential cross sections for the DY process measured in the muon channel, as functions of ${p_{\mathrm {T}}}$ (upper row) and ${\phi ^*}$ (lower row), for 15 $ < {m_{\mu \mu}} < $ 60 GeV (left) and 60 $ < {m_{\mu \mu}} < $ 120 GeV (right). The first bin of the ${p_{\mathrm {T}}}$ and ${\phi ^*}$ measurements starts at 0. The error bars on the data represent the quadratic sum of the statistical and systematic uncertainties. Theory predictions from the POWHEG NLO generator are also shown, using CT14 (blue) or CT14+EPPS16 (red). The boxes show the 68% confidence level (n)PDF uncertainty on these predictions. The ratios of predictions over data are shown in the lower panels, where the data and (n)PDF uncertainties are shown separately, as error bars around one and as coloured boxes, respectively. |
png pdf |
Figure 8-c:
Differential cross sections for the DY process measured in the muon channel, as functions of ${p_{\mathrm {T}}}$ (upper row) and ${\phi ^*}$ (lower row), for 15 $ < {m_{\mu \mu}} < $ 60 GeV (left) and 60 $ < {m_{\mu \mu}} < $ 120 GeV (right). The first bin of the ${p_{\mathrm {T}}}$ and ${\phi ^*}$ measurements starts at 0. The error bars on the data represent the quadratic sum of the statistical and systematic uncertainties. Theory predictions from the POWHEG NLO generator are also shown, using CT14 (blue) or CT14+EPPS16 (red). The boxes show the 68% confidence level (n)PDF uncertainty on these predictions. The ratios of predictions over data are shown in the lower panels, where the data and (n)PDF uncertainties are shown separately, as error bars around one and as coloured boxes, respectively. |
png pdf |
Figure 8-d:
Differential cross sections for the DY process measured in the muon channel, as functions of ${p_{\mathrm {T}}}$ (upper row) and ${\phi ^*}$ (lower row), for 15 $ < {m_{\mu \mu}} < $ 60 GeV (left) and 60 $ < {m_{\mu \mu}} < $ 120 GeV (right). The first bin of the ${p_{\mathrm {T}}}$ and ${\phi ^*}$ measurements starts at 0. The error bars on the data represent the quadratic sum of the statistical and systematic uncertainties. Theory predictions from the POWHEG NLO generator are also shown, using CT14 (blue) or CT14+EPPS16 (red). The boxes show the 68% confidence level (n)PDF uncertainty on these predictions. The ratios of predictions over data are shown in the lower panels, where the data and (n)PDF uncertainties are shown separately, as error bars around one and as coloured boxes, respectively. |
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Figure 9:
Forward-backward ratios for 15 $ < {m_{\mu \mu}} < $ 60 GeV (left) and 60 $ < {m_{\mu \mu}} < $ 120 GeV (right). The error bars on the data points represent the quadratic sum of the statistical and systematic uncertainties. The theory predictions from the POWHEG NLO generator are also shown, using CT14 [51] (blue), CT14+EPPS16 [14] (red), or CT14+nCTEQ15WZ [19] (green) PDF sets. The boxes show the 68% confidence level (n)PDF uncertainty in these predictions. The ratios of predictions over data are shown in the lower panels, where the data and the (n)PDF uncertainties are shown separately, as error bars around one and as coloured boxes, respectively. |
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Figure 9-a:
Forward-backward ratios for 15 $ < {m_{\mu \mu}} < $ 60 GeV (left) and 60 $ < {m_{\mu \mu}} < $ 120 GeV (right). The error bars on the data points represent the quadratic sum of the statistical and systematic uncertainties. The theory predictions from the POWHEG NLO generator are also shown, using CT14 [51] (blue), CT14+EPPS16 [14] (red), or CT14+nCTEQ15WZ [19] (green) PDF sets. The boxes show the 68% confidence level (n)PDF uncertainty in these predictions. The ratios of predictions over data are shown in the lower panels, where the data and the (n)PDF uncertainties are shown separately, as error bars around one and as coloured boxes, respectively. |
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Figure 9-b:
Forward-backward ratios for 15 $ < {m_{\mu \mu}} < $ 60 GeV (left) and 60 $ < {m_{\mu \mu}} < $ 120 GeV (right). The error bars on the data points represent the quadratic sum of the statistical and systematic uncertainties. The theory predictions from the POWHEG NLO generator are also shown, using CT14 [51] (blue), CT14+EPPS16 [14] (red), or CT14+nCTEQ15WZ [19] (green) PDF sets. The boxes show the 68% confidence level (n)PDF uncertainty in these predictions. The ratios of predictions over data are shown in the lower panels, where the data and the (n)PDF uncertainties are shown separately, as error bars around one and as coloured boxes, respectively. |
Tables | |
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Table 1:
Range of systematic uncertainties in percentage of the cross section, given separately for 15 $ < {m_{\mu \mu}} < $ 60 and 60 $ < {m_{\mu \mu}} < $ 120 GeV. Systematic uncertainties for the three mass bins above 120 GeV fall in the range given for 15 $ < {m_{\mu \mu}} < $ 60 GeV. For the theoretical component of acceptance and efficiency, the systematic uncertainty related to efficiency alone (for fiducial cross sections) is given between parentheses. |
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Table 2:
$\chi ^2$ values between the data and the POWHEG predictions and associated probability, from the fiducial cross sections, when experimental and theoretical bin-to-bin correlations are taken into account. The integrated luminosity uncertainty is included in the experimental uncertainties. |
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Table 3:
$\chi ^2$ values between the data and the POWHEG predictions and associated probability, from the full phase space cross sections, when experimental and theoretical bin-to-bin correlations are taken into account. The integrated luminosity uncertainty is included in the experimental uncertainties. |
Summary |
Differential cross section measurements of the Drell-Yan process in the dimuon channel in proton-lead collisions at ${\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 8.16 TeV have been reported, including the transverse momentum (${p_{\mathrm{T}}}$) and rapidity dependencies in the Z boson mass region (60 $ < m_{\mu\mu} < $ 120 GeV). In addition, for the first time in collisions including nuclei, the ${p_{\mathrm{T}}}$ and rapidity dependence for smaller masses 15 $ < m_{\mu\mu} < $ 60 GeV have been measured. The dependence with ${\phi^*}$ (a geometrical variable that highly correlates with dimuon ${p_{\mathrm{T}}}$ but is determined with higher precision) for both 15 $ < m_{\mu\mu} < $ 60 GeV and 60 $ < m_{\mu\mu} < $ 120 GeV and the mass dependence from 15 to 600 GeV have been presented, also for the first time in proton-nucleus collisions. Finally, forward-backward ratios have been built from the rapidity-dependent cross sections for ${y_{\mathrm{CM}}} > $ 0 to ${y_{\mathrm{CM}}} < $ 0 in both mass regions, highlighting the presence of nuclear effects in the parton distribution functions. Results for 60 $ < m_{\mu\mu} < $ 120 GeV are the most precise to date, featuring smaller uncertainties than the theoretical predictions, and provide novel constraints on the quark and antiquark nuclear parton distribution functions (nPDFs). Measurements in the lower mass range 15 $ < m_{\mu\mu} < $ 60 GeV give access to a new phase space for nPDF studies, extending to lower longitudinal momentum fraction $x$ and lower energy scale $Q^2$. The ${p_{\mathrm{T}}}$- and ${\phi^*}$ -dependent results are also very sensitive to the details of model details, such as soft quantum chromodynamics phenomena, which they may help to better understand in pPb collisions. |
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Compact Muon Solenoid LHC, CERN |